It was illustrative of how, when you gag all demons and take the public knowledge premises seriously, it is nigh impossible to actually disprove them, and even removing the gag it is rather difficult. Someone who read this fic without knowledge of Daevinity could very well end up not actually sure whether demons can really take souls or not.

And even viewpoint character's experiments are not enough; if demons have a way of detecting whether someone's soul has been taken or not, they could in fact all play along to convince people that selling souls is alright. And they could also be faking their task restrictions - say, it could be the case that they can actually lie about things they make when they produce posthumous works and what-have-you, just to convince more people to part with their souls.

If the protagonist knew of the AI box experiment or knew a Maitimo, there would be no reason to assume demons have superhuman persuasion just because they sometimes talk some people out of their souls. Apparently this enters public knowledge some time between 2030 and 2180, because the protagonist isn’t the only one to make this mistake.